java 网络编程-tcp/udp

--转自：http://blog.csdn.net/nyzhl/article/details/1705039

直接把代码写在这里，解释看这里吧：http://blog.csdn.net/nyzhl/article/details/1705039

Java UDP网络编程主要通过 DatagramSocket和DatagramPacket 两个类实现的，下面是一个示例程序，
Server监听UDP 2000端口并把收到的Long类型数值打印出来
Client则通过输入获得Long类型的数值，并把它发给Server

Server：

package com.sas ;
import java.net.*;
import java.io.*;

public class DatagramServer {
    public static void main (String[] args) {
        DatagramSocket ds = null;
        try {
            ds = new DatagramSocket(2000);
        }
        catch (SocketException e) {
            e.printStackTrace();
            System.exit(-1);
        }
        byte[] buffer = new byte[1024];
        DatagramPacket dp = new DatagramPacket(buffer,buffer.length);
        while (true) {
            DataInputStream in = new DataInputStream (
                new ByteArrayInputStream (buffer)
            );
            try {
                ds.receive(dp);
                System.out.println(in.readLong());
                in.close();
            }
            catch (IOException e) {
                e.printStackTrace();
                continue;
            }
        }
        //ds.close(); JDK提示"无法访问的语句"
        //因为前面是死循环，无论如何也执行不到后面的语句
    }
}

Client：

package com.sas;
import java.net.*;
import java.io.*;

public class DatagramClient {
    public static void main (String[] args) {
        DatagramSocket ds = null;
        try {
            ds = new DatagramSocket();
        }
        catch (SocketException e) {
            e.printStackTrace();
            System.exit(-1);
        }
        System.out.println("输入一个数字：");
        BufferedReader typeReader = new BufferedReader (
            new InputStreamReader(System.in)
        );
        long data = 0;
        while(true) {
            ByteArrayOutputStream bytesOut = new ByteArrayOutputStream();
            DataOutputStream dataOut = new DataOutputStream (bytesOut);
            try {
                data = Long.parseLong(typeReader.readLine());
                dataOut.writeLong(data);
                dataOut.flush();
                byte[] buffer = bytesOut.toByteArray();
                DatagramPacket dp = new DatagramPacket(
                    buffer,
                    buffer.length,
                    new InetSocketAddress("127.0.0.1",2000)
                );
                ds.send(dp);
                dataOut.close();
                bytesOut.close();
            }
            catch (SocketException e) {
                System.err.println("Socket Error!");
                continue;
            }
            catch (IOException e) {
                System.err.println("IO Error!");
                continue;
            }
            catch (Exception e) {
                e.printStackTrace();
                continue;
            }
        }
        //ds.close(); JDK提示"无法访问的语句"
        //因为前面是死循环，无论如何也执行不到后面的语句
    }
}

TCP实现：

client:

package com.sas;

import java.io.OutputStreamWriter;
import java.net.Socket;

public class TCPClient {
    public static void main(String[] args) throws Exception {
        Socket s = new Socket("127.0.0.1",2000);
        OutputStreamWriter w = new OutputStreamWriter(s.getOutputStream());
        w.write("Hello服务器");
        w.flush();
        w.close();
        s.close();
    }
}

server:

package com.sas;
import java.io.InputStreamReader;
import java.net.ServerSocket;
import java.net.Socket;

public class TCPServer {
    public static void main(String[] args) throws Exception {
        ServerSocket ss = new ServerSocket(2000);
        while(true) {
            Socket s = ss.accept();
            System.out.println("A client has heen connected.");
            InputStreamReader r = new InputStreamReader(s.getInputStream());
            int c = 0;
            while((c=r.read())>-1) {
                System.out.print((char)c);
            }
            System.out.println();
            r.close();
            s.close();
        }
    }
}